Restricter



NOV. 27, 1951 w KUNZOG 2,576,610

RESTRICTER Filed April 10, 1944 INVENTOR THEODORE m/Ku/vzoe ATTORNPatented Nov. 27, 1951 UNiTED STATES PATENT GFFICE RESTRICTE'R TheodoreKunzog, Dayton, Ohio, assignorto General Motors Corporation,Detroit,..Mich., a. corporation of Delaware Application April 10, 1944,Serial No. 530,435

lClaim. 1

This inventionrelates .to expansion systems andis particularly;concerned with. restricters used in refrigeration. systems.

It is the primeobject of theinvention to provide .a restricter. ormetering devicefor a reirigeration system or the like that provides amultiplicity of capillary passages therethrough thereby, eliminating thepossibility of the restricter becoming inoperative due to cloggingcaused by extraneous matter passing therethrough.

In carrying .out the above object it is a further object to form saidrestricter from sintered non compacted metal powder which providesamultiplicity of tortuous, interconnecting passages of capillary sizetherethroughk Further objectsand advantages of the present inventionwill be apparent from the following description, reference being had tothe accompanying drawings wherein preferred embodiments .of the presentinvention are clearly shown.

In the drawings:

Fig; 1 is a diagrammatic view of'a refrigera tion system such as is usedin a household refrigerator;

Fig.2 is an enlarged sectional view of the restricterassembly used inthe refrigerationasystem;

Fig. 3 is "a view of the restricter perse on a greatly enlarged scale;and,

Fig.4 is a section through line 4-41of Fig. 3

showing a cross section of the restricter and'indicating themultiplicity of capillary size passagesthrough a section thereof.

Expansion systems, suohas are used in household refrigerators include .arestricter, or device of similar function which, due to the highpressure drop-therethroughcauses rapid expansion of the refrigerant thatpasses therethrough thereby creating the cooling effect in'theevaporator. Heretofore these restricters have been made of severaldesigns, such as a predetermined length of .capillary tubing, and othersimilar types of designs all" providing a capillary passage whichpresents a high back pressureand which permits tremendous expansion ofthe refrigerant that finally passes therethrough. The prior'artrestricters all have the same disadvantage namely, the restricterhas a single passage which if 'cloggedby an extraneous piece of 'dirt inthe refrigerant causes the entire refrigerating system to becomeinoperative and which can not be dislodged without replacement of therestricter.

The present invention is directed to a restricter of unique design whichdue to the method by which it is formed produces a multiplicity ofcapillary passages having tortuous shapes which present. the, desiredback pressure on the refrigerant and likewise due to. the -manycapillary passages therein eliminates theprior art disadvantagedue tocloggingzsince if oneor more of the passages .areclogged it has littleornoeffect on the operation of the restricterlbecause there are such amultitudeof passages available. Further, since the passages-areinterconnecting the clogging of one -or=two passages at theentrancethereof does not necessarily change the pressure drop characteristics-ofthe restricter since theremainderof passages which are not clogged attheir entrances may be interconnected with theiclogged passages.

My improved restricter is formed'from sintered non-compacted metalpowders, suchas are described in the Davis Patent No. 2,157,596,. andOlt Patent No. 2,273,589, both assigned to the assignee of the presentinvention. These powders when sintered in .a non-compacted conditionpresent a highly porous materiahthe porosity of which may be readilycontrolled bythegrain size of the powders utilized,.and in thisconnection any-desired porosity may be obtained, the control-of theporosity forming no. portion of .this invention since this control mustnecessarily change in accordance with the back pressure desired. Inother. words, the grain. size and the length of. the restricter togetherwith its crosssection definitely determinesv the. pressure dropthrough.the. re-

stricter and these factors are best determined by trial. Metal powdersare available in any number of different grain sizes, for example, from.,to 300 mesh and the restricter can be satisfactorily madefromany ofthese-metal powders .if the proper balance in length and...diameter forthe grain size .of. powder is determined. In all cases the passagesthrough the restricterare of capillary size.

Referringparticularlyto the drawings, Fig. 1 shows adiagrammatichook-.upof a refrigerating system such as is used an ordinary householdrefrigerator.

In this system a'compressor 20 is driven by an electric motor 22, whichis suitably controlled by a thermostatic device, not shown. Therefrigerant compressed 'by the: compressor 28 passes through atube 24into a condenser 26 which may or may not include acooling fan incooperation therewith; The refrigerant after becoming condensed flowsinto a receiver 28 where it is held under pressure by a restricter 30.The portion of the refrigerant which passes through the restricter 30due to the pressure thereon expands many times its volume at the outletside of the restricter thereby causing the cooling effect which isobtained in the evaporator 32 after which the refrigerant is returnedthrough tube 34 to the compressor. This operation is cycled inaccordance with operation of the compressor. In other words, when thethermostat calls for a lowering of the temperature in the evaporator,the motor starts and the compressor compresses the refrigerant whichcauses a fiow through the restricter 30 whereby the evaporator is cooleddue to an expansion of the refrigerant passing through the restricter30. lowered sufficiently to satisfy the thermostat the motor 22 is cutoff and the system remains idle with a slower leakage of refrigerantthrough the restricter until the pressure is lowered on the highpressure side whereupon the temperature of the evaporator generallyrises and requires another cycling of the motor and compressor unit. Therestricter 30 is shown in more detail i Fig. 2, wherein the restrictertube 36 is shown in partial fragmentary form whereby the porous metal 38is visible therein. The tube 36 is sweated onto a tube 40 whichpreferably has a union greatly enlarged scale wherein the tube 35 whichis preferably formed from copper and the porous metal 38 is bonded tothe walls thereof due to the method of manufacture. In this instance asatisfactory restricter material may be bronze which is generally formedfrom bronze powder as described in the said Olt patent. The powder isfilled into the tube 36 in the substantially noncompacted condition. Thepowder is preferably spherical in cross section and is from 80 to 150mesh in size although other shapes of powder particles may be used.After the powder is filled into the tube 36 the assembly is placed in asintering furnace where it is heated to a temperature in theneighborhood of from 1500 to 1600 F. for a period of about one-half hourunder nonoxidizing conditions whereupon the metal powders sintertogether to form a homogeneous prous bronze which is metallurgicallybonded to the walls of the tube 36. This porous metal or porous bronzepresents many hundreds of tortuous passages of interconnecting charactertherethrough which passages are all of capillary size. Thus, when a tubeis utilized having a length, for example of 4", and an internal diameterof A a considerable body of porous metal is provided which creates ahigh pressure drop therethrough but still permits a metered fluid flowtherethrough.

Other metals can be used in the restricter, for example, the tube may benickel, steel, bronze, stainless steel or the like and the porous metalmay be copper coated iron, copper-nickel alloy, copper-zinc alloy or thelike. In each case care After the temperature has been.

iii)

4 must be taken to provide a material which is not in any waydeleteriously affected by chemical action of the refrigerant. This is animportant factor since, if any chemical action occurs between thematerial of either the tube or the porous metal and the refrigerant, therestricter may become valueless in a very short period of time. Thentoo, if any small quantity of moisture or oil gets in the refrigerantdifficulty may be experienced if an chemical reaction is possible.Therefore, restricter materials should be chosen which are chemicallynon-reactive with the refrigerant or with the impurities found in therefrigerant.

While the embodiments of the present invention as herein disclosed,constitute preferred forms, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows:

A device for use in connection with refrigeration systems and adapted tobe included in the high pressure refrigerant line thereof comprising, incombination, an elongated cupreous metal tube having a constantrelatively small cross section through an elongated portion of itsextent and having a larger cross section adjacent one end thereof, saidelongated portion of said tube comprising a restricter consisting of asintered porous bronze mass made from sintered noncompacted metal powderand integrally metallurgically bonded throughout its entire contactingextent to the inner walls of said tube, said mass providing amultiplicity of longitudinally extending tortuous passages ofinterconnecting extent and of capillary size through said tube forcausing a predetermined and desired pressure drop and resulting rapidexpansion of refrigerant which has passed therethrough, a large diameterplate joined to said tube at the large cross section portion thereof andincluding a thread at its outer periphery, a cup member adapted toengage said threaded portion, said cup member having complementarythreads thereon, and a porous bronze filter element made from sinterednoncompacted metal powder of relatively thin cross section and ofrelatively large radial extent clamped between said cup member and saidplate at the threaded portions thereof, said filter element beingpositioned adjacent the high pressure side of the restricter forremoving extraneous particles from the refrigerant prior to theirpassage through the restricter.

THEODORE W'. KU'NZOG.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,687,780 Neale Oct. 16, 19281,947,586 Fletcher Feb. 20, 1934 1,957,828 Greenwald May 8, 19342,198,612 Hardy Apr. 30, 1940 2,220,641 Davis Nov, 5, 1940 2,290,734Brassert July 21, 1942 2,297,817 Truxell, Jr., et al. Oct. 6, 19422,359,386 Reinsch Oct. 3, 1944

